I believe that an Ethical Hacker should know all the concepts of hacking, including picking locks.
I managed in just a couple of days of practice to become a fair lock picker.
There are some locks that are really easy, such as locker or drawer, and even some door locks are easy.
I like the MIT guide to Lock Picking it’s really comprehensive and explains how locks work and why you can pick them.
There are also some nice lock picking videos on youtube although they’re more about showing off than explain.
To get you started you can buy this cheap lock picks kit, I got it and it’s good enough for beginners. If you can’t afford the 5$ you can make lock picks yourself, it’s not that hard but it’s less effective.
And for the nice finale, sometimes good locks gives us a false sense of security, and sometimes you don’t even have to pick the lock: how to open a locked suitcase with a pen.
Let this be a lesson to you, sometimes in order to hack you don’t have to attack the lock, sometimes you can just get around it